1. Field of the Invention
This invention relates generally to the field of welding guns and, more particularly, to a welding gun having an improved switch which can be manually operated by a welding machine operator to initiate a welding process regardless of the orientation of the welding gun in the operator's hand.
2. Description of the Prior Art
Welding guns, especially those used for gas metal arc welding, normally have a trigger mechanism for operating a switch for starting and stopping a welding process. Typically, this trigger mechanism is a lever arrangement located on the handle of the gun near the arc end thereof. Most welding machine operators judge as convenient a trigger mechanism that depresses easily and has overtravel, because the operator wants both a low depression force to reduce fatigue and also overtravel to reduce sensitivity so that, when he must reposition his hand during long welds, the switch does not release to open the welding circuit and stop the welding process.
The position of the trigger mechanism on the handle of the welding gun is also important. The nature of some welding procedures often dictates that a trigger mechanism actuated from the top of the welding gun is most convenient. However, other welding procedures may dictate that a bottom actuated trigger is more convenient, while still other weld procedures make side triggers more convenient. Furthermore, some operators prefer to actuate the trigger with their thumb, while others prefer to use the other fingers of their hand.
In summary, a good welding gun trigger mechanism will have the following features:
A. Easily depressed. PA1 B. Overtravel to reduce sensitivity from opening. PA1 C. Be easily repositionable so that the trigger can be actuated from the top, sides or bottom of the handle of the welding gun.
To address feature C, above, some gun manufacturers have made provisions for repositioning the trigger mechanism with respect to the arc end of the gun. In some cases they have provided means which permit the handle to be disassembled and then reassembled in such a way that the position of the trigger on the handle is changed. In other cases, they have designed the welding gun so that the arc end can be repositioned with respect to the handle and the trigger; this result is normally accomplished by some sort of rotatable head tube and lock unit assembly. However, the flaws in both of these cases are obvious. In the first case, the gun must be dismantled to adjust the relative position of the trigger. The second case requires less effort, but the welding current must pass through a movable joint. Futhermore, to make and properly secure a good electrical connection often requires tools. Sometimes, this feature of making the trigger repositionable is accomplished by a combination of the two cases if the handle is disassembled to make the positioning arrangement operable. In another case, a separate trigger switch assembly is externally clamped to the welding gun. In such a case the trigger projects outwardly from the profile of the welding gun handle, the electrical conductors connecting the switch get in the way of the operator, and the switch itself is bulky and vulnerable to abuse.
These and other prior art welding guns with trigger mechanism are shown, for example, in U.S. Pat. Nos. 3,469,070, 3,596,049, 3,783,233 and 3,980,860. Furthermore, switches generally employing spring conductors are shown in U.S. Pat. Nos. 2,651,689, 3,706,864 and 3,743,798 and in French Pat. No. 1,372,023.
However, until the present invention, no one has made a welding gun having a switch that can be operated from any direction with overtravel, and without requiring dismantling of the gun or the use of tools. Nor is there available in the prior art any welding gun in which the trigger mechanism can be repositioned during actual welding.